FIELD-STUDY OF COMPENSATORY CHANGES IN UV-ABSORBING COMPOUNDS IN THE MUCUS OF THE SOLITARY CORAL FUNGIA-REPANDA (SCLERACTINIA, FUNGIIDAE) IN RELATION TO SOLAR UV-RADIATION, SEA-WATER TEMPERATURE, AND OTHER COINCIDENT PHYSICOCHEMICAL PARAMETERS

The relationship between coral UV-absorbing compounds (mycosporine-lik e amino acids, or MAAs) and solar UV radiation in the shallow coral re ef environment has been much debated. The presence of these compounds in the mucus of Fungiidae allowed the measurement of weekly compensato ry changes in the amount and composition of these compounds together w ith shifts in the wavelength of maximum absorbance (lambda(max)) in th e mucus of 11 specimens of Fungia repanda (Scleractinia:Fungiidae) dur ing 18 months of monitoring in situ in Tahiti. The corals received ful l sunlight within a topless cage (specimen depth, 1 m) located at the Arue lagoon (northern coast of Tahiti). The amount of UV-absorbing com pounds was found to be significantly and positively related to solar U V radiation, with a lag time of one week and with a corresponding long -wavelength shift in the maximum absorbance without lag, but was not s ignificantly related to sea-water temperature or to the volume of mucu s secreted. Analysis of mucus MAAs by high-performance liquid chromato graphy showed that the shift in lambda(max) could be related to an inc rease in three components: mycosporine-2-glycine, palythine and mycosp orine-glycine.